Collaborative voice controlled devices

ABSTRACT

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for collaboration between multiple voice controlled devices are disclosed. In one aspect, a method includes the actions of identifying, by a first computing device, a second computing device that is configured to respond to a particular, predefined hotword; receiving audio data that corresponds to an utterance; receiving a transcription of additional audio data outputted by the second computing device in response to the utterance; based on the transcription of the additional audio data and based on the utterance, generating a transcription that corresponds to a response to the additional audio data; and providing, for output, the transcription that corresponds to the response.

TECHNICAL FIELD

This specification generally relates to automated speech recognition.

BACKGROUND

The reality of a speech-enabled home or other environment—that is, onein which a user need only speak a query or command out loud and acomputer-based system will field and answer the query and/or cause thecommand to be performed—is upon us. A speech-enabled environment (e.g.,home, workplace, school, etc.) can be implemented using a network ofconnected microphone devices distributed throughout the various rooms orareas of the environment. Through such a network of microphones, a userhas the power to orally query the system from essentially anywhere inthe environment without the need to have a computer or other device infront of him/her or even nearby. For example, while cooking in thekitchen, a user might ask the system “how many milliliters in threecups?” and, in response, receive an answer from the system, e.g., in theform of synthesized voice output. Alternatively, a user might ask thesystem questions such as “when does my nearest gas station close,” or,upon preparing to leave the house, “should I wear a coat today?”Further, a user may ask a query of the system, and/or issue a command,that relates to the user's personal information. For example, a usermight ask the system “when is my meeting with John?” or command thesystem “remind me to call John when I get back home.”

SUMMARY

Hotwords may be used in order to avoid picking up utterances made in thesurrounding environment that are not directed to the system. A hotword(also referred to as an “attention word” or “voice action initiationcommand”) is a predetermined word or term that is spoken to invoke theattention of the system. In an example environment, the hotword used toinvoke the system's attention are the words “OK computer.” When thesystem detects that the user has spoken the hotword, the system enters aready state for receiving further user commands.

In speech-enabled environments, devices may be continuously listeningfor hotwords. When there are multiple devices in the same environmentthat are configured to respond to a particular hotword, any utteranceincluding the hotword may trigger all the devices and provide redundantresponses from the multiple devices. For example, Alice, Bob and Carlmay be looking for a restaurant to go to for lunch. Alice may say “OKComputer, find me restaurants nearby”. All three of their phones maysimultaneously provide a response, e.g., a list of restaurants. Toimprove user experience, it may be desirable for the phones tocommunicate with one another to provide different responses in acoordinated fashion similar to an actual conversation. Alice's phone mayprovide a list of nearby restaurants and Bob's phone may provide aresponse selecting one of the restaurants in the list of nearbyrestaurants provided by Alice's phone. Carl's phone may provide aresponse approving the selected restaurant based on Carl's review of therestaurant on social media.

According to one innovative aspect of the subject matter described inthis specification, a first computing device identifies one or moreother computing devices that are configured to respond to a particular,predefined hotword. The first computing device receives an utterancethat is spoken by a user. Before performing speech recognition on theaudio data that corresponds to the utterance, the first computing devicedetermines that the audio data includes the hotword, and that a secondcomputing device is already processing the audio. The first computingdevice receives the response outputted by the second computing device inresponse to the utterance. Based on this response and the utterance, thefirst computing device generates a response and provides the responsefor output. Thus the first computing device augments the response fromthe second computing device and provides a new response which canprovide additional information to the users.

In general, another innovative aspect of the subject matter described inthis specification may be embodied in methods that include the actionsof identifying, by a first computing device, a second computing devicethat is configured to respond to a particular, predefined hotword;receiving audio data that corresponds to an utterance; receiving atranscription of additional audio data outputted by the second computingdevice in response to the utterance; based on the transcription of theadditional audio data and based on the utterance, generating atranscription that corresponds to a response to the additional audiodata; and providing, for output, the transcription that corresponds tothe response.

These and other embodiments can each optionally include one or more ofthe following features. In some implementations, providing, for outputthe transcription that corresponds to the response comprises providingan initial portion of the transcription to a speech synthesizer of thefirst computing device; and providing, to the second computing device,(i) a remaining portion of the transcription and (ii) instructions tooutput the remaining portion of the transcription using a speechsynthesizer of the second computing device.

In some implementations, the actions further include before performingspeech recognition on the audio data that corresponds to the utterance:determining that the audio data that corresponds to the utteranceincludes the particular, predefined hotword; and receiving dataindicating that the second computing device is responding to the audiodata.

In some implementations, providing, for output, the transcription thatcorresponds to the response comprises providing the transcription thatcorresponds to the response to a speech synthesizer.

In some implementations, the audio data that corresponds to thesynthesized transcription is received by a third computing device thatis configured to generate a response based on the audio data thatcorresponds to the synthesized transcription, the transcription of theadditional audio data, and the utterance.

In some implementations, the actions further include after providing,for output, the transcription that corresponds to the response,receiving, by the first computing device, audio data that corresponds toa second utterance; based on the transcription of the additional audiodata, based on the utterance, and based on the second utterance,generating an additional transcription that corresponds to a response tothe audio data that corresponds to the second utterance; and providing,for output, the additional transcription.

In some implementations, the actions further include receiving dataindicating a type of speech synthesizer used by the second computingdevice to output the additional audio data, wherein a type of speechsynthesizer that received the transcription that corresponds to theresponse is different than the type of speech synthesizer used by thesecond computing device to output the additional audio data.

In some implementations, providing, for output, the transcription thatcorresponds to the response comprises providing the transcription to adisplay of the first computing device.

In some implementations, receiving data indicating that the secondcomputing device is responding to the audio data includes receiving,from the second computing device, a short range radio signal thatindicates that the second computing device is responding to the audiodata. In some implementations, receiving data indicating that the secondcomputing device is responding to the audio data includes receiving,from the second computing device and through a local network, dataindicating that the second computing device is responding to the audiodata. In some implementations, receiving data indicating that the secondcomputing device is responding to the audio data includes receiving,from a server, data indicating that the second computing device isresponding to the audio data.

In certain aspects, determining that the audio data that corresponds tothe utterance includes the particular, predefined hotword includes thesteps of extracting audio features of the audio data that corresponds tothe utterance; generating a hotword confidence score by processing theaudio features; determining that the hotword confidence score satisfiesa hotword confidence threshold; and based on determining that thehotword confidence score satisfies a hotword confidence threshold,determining that the audio data that corresponds to the utteranceincludes the particular, predefined hotword.

In some implementations, generating a transcription that corresponds toa response to the additional audio data comprises determining userinformation that is associated with the transcription of the additionalaudio data that is associated with a first user of the first computingdevice or with a second user of the second computing device; and whereinthe transcription is generated based on the user information.

In certain aspects, generating a transcription that corresponds to aresponse to the additional audio data comprises the actions of accessingdata that is associated with the transcription of the additional audiodata; and generating the transcription based on the accessed data.

The actions further include determining a location of the firstcomputing device, and generating the transcription based on the locationof the first computing device. The actions further include providing, tothe second computing device or to a server, the audio data thatcorresponds to the utterance in response to receiving data indicatingthat the second computing device is responding to the audio data.

In some implementations, the actions further include generating a firstaudio fingerprint of the audio data that corresponds to the utterance;receiving, from the second computing device, a second audio fingerprintof the audio data that corresponds to the utterance; comparing the firstaudio fingerprint to the second audio fingerprint; and based oncomparing the first audio fingerprint to the second audio fingerprint,determining that the audio data received by the first computing devicecorresponds to the audio data received by the second computing device.

In some implementations, further actions include receiving, from thesecond computing device or a server, a transcription of the audio datathat corresponds to the utterance, wherein generating the transcriptionthat corresponds to the response to the additional audio data is basedfurther on the transcription of the audio data that corresponds to theutterance.

In some implementations, the first computing device and the secondcomputing device are able to detect short range radio communicationsfrom each other.

In some implementations, the first computing device and the secondcomputing device are co-located.

Other embodiments of this aspect include corresponding systems,apparatus, and computer programs recorded on computer storage devices,each configured to perform the operations of the methods.

Particular embodiments of the subject matter described in thisspecification can be implemented so as to realize one or more of thefollowing advantages. First, a collaborative voice controlled devicesystem can make conversational search smarter and more natural byseamlessly providing multiple and sequential responses in a coordinatedfashion similar to an actual conversation. Before providing a responseto a query, a device may process the available information to generate aresponse. Each device can provide a unique response which can add to theconversation and can be user-specific or location-specific. The devicemay either provide the unique response or pass the information toanother device. Providing information to another devices allows thedevice to make conversations more human-like by intentionally leavingout parts of the unique response so that other devices may complete theresponse. Second, a collaborative voice controlled device system canresolve the problem of multiple devices responding to the same query ina nearly identical manner. For example, communication between thedevices allows the devices to determine how and when the devices respondto the query. This reduces the wastage of computing resources andbattery power by avoiding redundant output. Third, the collaborativevoice controlled device system can be used to improve speech processingby using multiple devices with different microphones at differentlocations to process audio data to get a more accurate transcription ofthe audio data.

The details of one or more embodiments of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages of thesubject matter will become apparent from the description, the drawings,and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an example system for collaboration betweenmultiple voice controlled devices.

FIG. 2 is a diagram of an example process for collaboration betweenmultiple voice controlled devices.

FIG. 3 shows an example of a computing device and a mobile computingdevice.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

FIG. 1 is a diagram of an example system 100 for collaboration betweenmultiple voice controlled devices. In general, the system 100illustrates a user Alice speaking an utterance 102 “OK computer, find mea good steakhouse nearby for lunch” that is detected by computingdevices 104 a and 104 b. Computing device 104 a processes the utteranceand provides a response “Al's steakhouse at 123 Main Street has goodreviews.” Based on the utterance 102 and the response provided bycomputing device 104 a, computing device 104 b generates and provides afollow-up response “Al's is very busy right now, let's try Lone StarSteakhouse at 4 Main Street instead. Bob likes it a lot.”

In more detail, the sequence of events in FIG. 1 begins at stage A. Thecomputing devices 104 a and 104 b identify each other and othercomputing devices that are configured to respond to a particular,predefined hotword. In some implementations, the computing devicesidentify each other by searching the local network for other computingdevices that are configured to respond to the hotword. For example,computing device 104 b may search the local area network, and mayidentify computing device 104 a as another computing device that isconfigured to respond to the hotword.

In some implementations, the computing devices identify other computingdevices that are configured to respond to the hotword by identifying theuser who is logged into each device. In some implementations, and inthis example, computing device 104 a may be associated with the userAlice and computing device 104 b may be associated with a user Bob. Inthis case, Alice may be logged into computing device 104 a and Bob maybe logged into computing device 104 b. Alice and Bob may be a part of agroup of users with associated devices that may be configured to respondto a particular, predefined hotword. The group of users may be a groupof co-workers at a company, or a group of friends. Each computing devicemay share information that is related to the user who is logged into theparticular computing device, such as a user identifier.

In some implementations, both computing devices 104 a and 104 b may beassociated with the same user. For example, Alice may be logged intocomputing devices 104 a and 104 b. Alice may have the computing device104 a in her hand. The computing device 104 b may be a home assistantlocated on a table. Computing device 104 a detects computing devices 104b and each computing device shares information that is related to theuser who is logged into the computing device, such as a user identifier.

In some implementations, once the computing device 104 b has identified104 a as a computing devices that is configured to respond to the samehotword, the computing devices 104 a and 104 b may share and store theirrespective device identifiers 106 and 108. The identifiers may be basedon a type of device, an IP address of the device, a MAC address, a namegiven to the device by a user, or any combinations thereof. For example,the device identifier 106 for computing device 104 a may be “Alicephone”. The device identifier 108 for computing device 104 b may be “Bobphone”. The computing devices 104 a and 104 b have respective devicegroups 110 and 112 where the computing devices store the deviceidentifiers.

In some implementations, there may be more than two computing devicesthat are configured to respond to the particular hotword. Each computingdevice may identify the other computing devices that are configured torespond to the particular hotword, and may store the device identifiersfor the other computing devices in the device group.

In some implementations, the computing devices may be co-located suchthat they share a same location or place. The computing devices may bewithin a predetermined distance of each other, or within the same room.The computing devices may be in the same acoustic environment. In someexamples, the computing devices may be co-located virtually, e.g., whenthe computing devices participate in a telephone or video conference.

In some implementations, the computing devices may identify othercomputing devices that are configured to respond to the hotword throughshort range communication such as the Bluetooth protocol or theBluetooth Low Energy (BLE) protocol. For example, the computing device104 a may transmit a signal through short range communication searchingfor other computing devices that are configured to respond to thehotword. The computing devices may be located within a particulardistance of each other, such as ten meters, as determined by GPS orsignal strength. The first computing device may detect a strength of asignal being transmitted by the second computing device and translatethat to a corresponding distance. The computing devices may employ oneof these techniques or a combination of them to identify other computingdevices that are configured to respond to the hotword.

In this example and in stage B, Alice speaks the utterance 102, “OKcomputer, find me a good steakhouse nearby for lunch,” in the vicinityof the computing devices 104 a and 104 b. The utterance 102 is detectedby microphones 114 and 116 of computing devices 104 a and 104 brespectively.

The respective microphones 114 and 116 of the computing devices 104 aand 104 b provide audio data to respective audio subsystems 118 and 120.The respective audio subsystems 118 and 120 may buffer, filter, anddigitize the audio data. In some implementations, the computing devicemay also perform endpointing on the audio data. The audio subsystems 118and 120 may include audio buffers to store filtered and digitized audiodata.

In stage C, the respective audio subsystem 118 and 120 of each computingdevice 104 a and 104 b provide the processed audio data to respectivehotworders 122 and 124. The respective hotworders 122 and 124 comparethe processed audio data to known hotword data and compute respectivehotword confidence scores that indicate the likelihood that theutterance 102 includes a hotword 126.

The hotworder 124 of computing device 104 b may extract audio featuresfrom the processed audio data such as filterbank energies ormel-frequency cepstral coefficients. The hotworder 124 may useclassifying windows to process these audio features such as by using asupport vector machine or a neural network. Based on the processing ofthe audio features, if the hotworder 124 of computing device 104 bcomputes a hotword confidence score that exceeds a threshold hotwordconfidence score, the computing device 104 b determines that theutterance 102 includes the hotword 126. Similarly, the hotworder 122 ofcomputing device 104 a may determine that the utterance 102 includes thehotword 126.

In some implementations, one or more of the computing devices sends theprocessed audio data to a server and the server computes a hotwordconfidence score. In this instance, the server includes a hotwordersimilar to hotworders 122 and 124. The hotworder on the server maydetermine that the utterance 102 includes the hotword and sends thenotification to the one or more computing devices.

In some implementations, the system determines that the audio dataincludes the hotword without performing speech recognition on the audiodata.

In some implementations, each computing device may generate audiofingerprints of the received audio data. Computing device 104 b maygenerate a first audio fingerprint of the audio data that corresponds tothe utterance detected by microphone 114 of the computing device 104 a.The computing device 104 a may receive a second audio fingerprint of theaudio data that corresponds to the utterance detected by microphone 116of the computing device 104 b. The audio fingerprints may be compared todetermine if the computing devices 104 a and 104 b are responding to thesame utterance.

In some implementation, the audio data from the computing devices may besent to a server. The server may include an audio fingerprinting moduleto generate the audio fingerprints and perform the comparison. In someimplementations, the computing devices may also send a device identifierwith the audio data. In some implementations, the computing devices mayalso send location information associated with the computing deviceswith the audio data.

In stage D, the speech-enabled system 100 identifies one of thecomputing devices as the device that the utterance 102 is intended for.In this example, Alice may speak the utterance 102 towards the computingdevice 104 a, which is in her hand. The computing device 104 a isidentified as the computing device that the utterance 102 is intendedfor. The computing device 104 a notifies the other devices that weretriggered by the utterance 102 that it will be processing the audiodata. In this example, computing device 104 a sends response indicator128 indicating that it is responding to the audio data corresponding tothe utterance 102 to computing device 104 b.

In some implementations, the response indicator 128 indicating that 104a is responding to the audio data may be an ultrasonic or audible audiosignal, or a short range radio signal such as Bluetooth. The signal isreceived by 104 b and any other computing devices in the vicinity. Insome implementations, the notification signal may include a particularfrequency and/or pattern. For example, a notification signal may betwenty kilohertz to indicate that the second computing device willperform speech recognition on the audio data.

In some implementations, the response indicator 128 indicating that 104a is responding to the audio data may be received by 104 b through alocal network. In some implementations, the response indicator 128indicating that 104 a is responding to the audio data may be received by104 b through a server.

In some implementations, determining which device initially responds toa user utterance may involve determining which device is nearest to theuser. The loudness of the audio data received by the computing devicemay reflect a distance between the computing device and the source ofthe audio. For direct path signal propagation, the loudness isapproximately inversely proportional to the square of the distancebetween the source and the receiver.

In some implementations, the computing devices may calculate a loudnessscore for the audio data using one or a combination of the followingtechniques. One technique may be to calculate the sound pressure orsound pressure level as received by the microphone when the user isspeaking the utterance. The higher the sound pressure or sound pressurelevel, the higher the loudness. A second technique is to calculate theroot mean square of the audio data. The higher the root mean squarevalue of the audio data, the higher the loudness. A third technique isto calculate the sound intensity of the audio data. The higher the soundintensity of the audio data, the higher the loudness. A fourth techniqueis to calculate the sound power of the audio data. The higher the soundpower, the higher the loudness. The computing device with the highestloudness score may be identified as the computing device which respondsinitially to the utterance 102.

In some implementations, determining which device initially responds toa user utterance may comprise determining which device receives theclearest audio data. Each computing device may calculate a clarity scorewhich may be determined based on the signal-to-noise-ratio of the audiodata associated with the utterance 102. The computing device with thehighest clarity score may be identified as the computing device whichresponds initially to the utterance 102.

In some implementations, determining which device initially responds toa user utterance may comprise performing speaker identification on theaudio data corresponding to the utterance 102. This may involveproviding the audio data to the respective speaker identificationmodules 154 and 156 of computing devices 104 a and 104 b. The speakeridentification modules 154 and 156 may be implemented in software thatruns on a processor. The speaker identification modules 154 and 156analyze the audio data to calculate a respective speaker identityconfidence score indicating a confidence that the identity of thespeaker matches the user associated with the computing device. Forexample, speaker identification module 154 of computing device 104 a maycalculate a confidence score of 0.8, and speaker identification module156 of computing device 104 b may calculate a speaker identificationconfidence score of 0.05, indicating a greater confidence that thespeaker is Alice.

In some implementations, the computing devices may use one of thesescores or a combination of them to determine a total confidence score.The total confidence score may be used to identify the computing devicethat initially responds to the user utterance 102. In someimplementations, each computing device may transmit the respectivescore, or combination of scores and the respective device identifier tothe other computing devices in the device group.

In some implementations, each computing device may use a score comparerto compare the total confidence scores of all the computing devices thatare configured to respond to the hotword. The computing device with thehighest total confidence score may initiate speech recognition on theaudio data following the hotword. A computing device that does not havethe highest total confidence score may wait for data indicating thatanother computing device has begun processing the audio data.

In some implementations, determining which device initially responds toa user utterance may comprise analyzing the settings of the computingdevice. For example, if the utterance is in French and there is onephone with French language settings in the vicinity, it is probably thecomputing device that the utterance was intended for.

In some implementations, determining which device initially responds toa user utterance may be done by analyzing the semantics of the commandor the query included in the utterance and correlating it with the stateand information of the computing devices. For example, if the query is“Who am I meeting with at two o'clock?” the speech-enabled system maydetermine that the query is intended for the computing device which issynchronized with a calendar, and has an appointment at two o'clock.

In stage E, the computing device 104 a processes the audio data thatcorresponds to the utterance 102. The audio data may be provided to aspeech recognizer 130, which may perform speech recognition on theportion of the audio data that follows the hotword. In this example, thespeech recognizer 130 may identify the words “find me a good steakhousenearby for lunch” and identify and execute the command.

In some implementations, the computing device 104 a may send the portionof the audio data following the hotword to a server. The server mayinclude a speech recognizer similar to the speech recognizer 130. Thespeech recognizer included in the server may perform speech recognitionand provide a transcription of the audio data to the computing device104 a. The computing device 104 a can then identify the words andexecute the command.

In some implementations, the computing device 104 a may generate aresponse to the audio data by accessing data associated with the audiodata. In this example, the computing device 104 a identifies the command“find me a good steakhouse nearby for lunch” in the utterance 102, andmay perform a web search to find steakhouses nearby. The computingdevice 104 a may also access customer reviews from the web to select asteakhouse, and to generate a transcription 132 corresponding to theresponse “Al's steakhouse at 123 Main Street has good reviews”.

In stage F, the computing device 104 a provides as output the generatedresponse to the audio data associated with the utterance 102. In someimplementations, this includes providing the transcription 132 thatcorresponds to the response to a speech synthesizer 134. The output ofthe speech synthesizer may be provided to a speaker 136 of the computingdevice. In this example the computing device 104 a provides, as output,the additional audio data 138 “Al's steakhouse at 123 Main Street hasgood reviews.”

In some implementations, the transcription 132 that corresponds to theresponse may be sent to a display 140 of the computing device 104 a.

In stage G, computing device 104 b sends the transcription 132 thatcorresponds to the response to computing device 104 b and any otheridentified computing devices.

In some implementations, one or more of the computer devices may includea privacy module that manages or filters the data being transmitted orreceived based on user settings or preferences.

In stage H, computing device 104 b processes the audio datacorresponding to the utterance 102 and the transcription 132 of theadditional audio data provided by computing device 104 b, and generatesa new transcription that corresponds to a response. In this example,computing device generates a response based on the command “find me agood steakhouse nearby for lunch” and the response provided by computingdevice 104 a, “Al's steakhouse at 123 Main Street has good reviews”.

In some implementations, the computing device 104 b may generate aresponse based on user information 142 that is associated with the audiodata. The user information may be associated with a user of thecomputing device (e.g., calendar, contacts, media files, personalpreferences, etc.). In this example, based on the command “find me agood steakhouse nearby for lunch” and the response provided by computingdevice 104 a, “Al's steakhouse at 123 Main Street has good reviews”, thecomputing device 104 b may access an online reservation system on theinternet and may access Bob's restaurant reviews or personal preferencesto generate a transcription corresponding to the response “Al's is verybusy right now, let's try Lone Star Steakhouse at 4 Main Street instead.Bob likes it a lot.”

In some implementations, computing device 104 b may receive atranscription of the audio data that corresponds to the utterance 102,and use this transcription in addition to the transcription of theresponse provided by computing device 104 b and the audio datacorresponding to the utterance. This may help in cases when computingdevice 104 b may be further away from the user speaking the utterance.Since computing device is closer to the user, it may provide a moreaccurate transcription of the utterance 102. This also eliminates theneed to perform speech recognition twice on the same audio data.

In stage I, the computing device 104 b provides the generated output inresponse to the utterance 102 and the additional audio data provided bycomputing device 104 a. In some implementations, this includes providingthe transcription that corresponds to the response to a speechsynthesizer 144. The output of the speech synthesizer may be provided toa speaker 146 of the computing device 104 b. In this example thecomputing device 104 a provides, as output, the utterance 148 “Al's isvery busy right now, let's try Lone Star Steakhouse at 4 Main Streetinstead. Bob likes it a lot”.

In some implementations, providing, for output, the transcription thatcorresponds to the response comprises providing the transcription to adisplay 150 of the computing device 104 a.

In some implementations, the parameters covering the voice produced bythe speech synthesizer (e.g., pitch, tone, accent, speed, inflection,etc.) may be adjusted. This allows for the creation of custom voices foreach computing device, improving user experience. The speech synthesizermay use a form of machine learning to generate the parametricrepresentation of speech to synthesize the speech. For example, a neuralnetwork may be used to generate the speech parameters.

In some implementations, one or more of the computing devices may followan initial response with a question or a prompt for the user to respondto before proceeding further. For example, if Alice speaks the utterance“OK computer, find me a good restaurant nearby for lunch”, Alice'sdevice may provide a list of restaurants nearby. Bob's device may accessBob's personal information and provide the response “Bob lovesArgentinian steak, there are a lot of good steakhouses nearby. Would youlike to try one?” One or more of the computing devices may wait for aresponse to the question and continue based on the response. Uponreceiving the response “Yes”, Bob's device might provide a follow-upresponse “Rural Society on 123 Madison Avenue has good reviews.”

In some implementations, the collaborative voice-controlled devicesystem may have more than two devices. For example, a group of threeusers Alice, Bob and Carl may be trying to obtain directions to a nearbypark and each may have their own device. Alice speaks the utterance “OKcomputer, give me directions to Prospect Park”. Alice's device mayaccess Alice's personal information, which indicates that she usuallyuses public transit. Alice's device may use that information, along withthe information obtained from a public transit web tool to provide theresponse, “There's a train leaving from Carol Square Station in 12minutes, it arrives at Prospect Park Station at 4:59 pm. It's a 4 minutewalk to Carol Square Station, and a 5 minute walk from Prospect ParkStation to the entrance of Prospect Park.” Bob's device may receive thisresponse through a network. In generating a response, Bob's device mayaccess Bob's personal information and see that Bob usually prefers todrive, and that he has parked his car at a nearby garage. The devicesmay detect the location change to the garage and discussion among Alice,Bob, and Carl to drive instead of take public transportation. Bob'sdevice may use a web map search tool to provide driving directions tothe park. During the drive, Carl's device may receive the directionsthrough the network and may access a real-time traffic tool to determinethat there is a faster route and provide a response, “If you take MainSt instead of Rock Rd, it will be 5 minutes faster.”

In some implementations, before providing a response, the devices maycollaborate with each other to generate more complete and relevantresponses. This may be done by using the available information, andsharing users' personal information provided a user selected to sharepersonal information beforehand. For example, if Alice says “OKcomputer, find me a good restaurant nearby”, all the devices may beginto process the query before any response is provided. Bob's phone maysend data to the other devices indicating that Bob is a vegetarian. Thisallows the devices to tailor their responses to only providevegetarian-friendly restaurant options.

In some implementations, the devices can either provide a response orpass the information to another device. Conversations may be made morehuman-like or humorous by intentionally coordinating the responses, orby leaving out parts of a response by a device, to be completed by otherdevices. For example, in the above example, where Bob's phone has shareddata indicating that Bob is a vegetarian, in response to “Shall we tryAl's Steakhouse on 123 Main Street?”, Alice's phone does not provide aresponse and waits for Bob's phone to provide the response “Are steaksvegetarian?”

FIG. 2 is a diagram of an example process 200 for collaboration betweenmultiple voice controlled devices. The process 200 may be performed by acomputing device such as the computing devices 104 a and 104 b fromFIG. 1. The process 200 determines that a second computing device isprocessing an audio utterance, and receives a transcription of aresponse to the utterance. The process 200 uses the utterance andtranscription of the response to generate a response.

The first computing device identifies a second computing device that isconfigured to respond to a particular, predefined hotword (210). In someimplementations, the first computing device may do this by periodicallytransmitting an ultrasound or radio signal that requests a response. Forexample, the first computing device may transmit an ultrasound that is20.5 kilohertz when searching for computing devices that recognizehotwords. In response, computing devices that receive the 20.5 kilohertzultrasound may respond with a twenty-one kilohertz ultrasound. In someimplementations, the ultrasonic or radio signal can be encoded withinformation identifying the first computing device.

In some implementations, the first computing device may identify othercomputing devices that belong to the same user. While setting up a newcomputing device, part of the setup procedure may be to identify othercomputing devices that belong to the same user. This may be accomplishedby detecting other devices that the user is logged into. Once the firstcomputing device identifies another computing device, the computingdevices may exchange data using an ultrasonic frequency signal thatencodes a bit stream so that the computing devices can exchange datawhen identifying a hotword.

The ultrasonic frequency signal may be transmitted through a speaker.For example, a user may be setting up a home assistant and part of theset up process is to search for other computing device that are nearbyand that respond to hotwords. The home assistant may identify a phoneand a tablet that the user is logged into. As an example, thethermostat, phone, and tablet may exchange data using an ultrasonicsignal upon identifying that each are co-located in a same room. Theultrasonic signal may include a bit stream identifying each of thedevices. The devices may use the ultrasonic channel upon detection of ahotword.

In some implementations, the computing devices may identify othercomputing devices that are configured to respond to the hotword byidentifying computing devices that are configured to respond when thehotword is spoken by the same user through speaker identification. Forexample, computing devices 104 a and 104 b may be configured to respondto the voice of Alice when Alice speaks the hotword. The computingdevices share the speaker identification information by providing a useridentifier for Alice to each other.

A user speaks the utterance and a microphone of the first computingdevice receives the audio data of the utterance (220). The firstcomputing device processes the audio data by buffering, filtering,endpointing, and digitizing the audio data. As an example, the user mayutter “OK computer” and the microphone of the first computing devicereceives the audio data that corresponds to “OK computer.” An audiosubsystem of the first computing device samples, buffers, filters, andperforms endpointing on the audio data for further processing by thefirst computing device.

In some implementations, the first computing device determines that theaudio data that corresponds to the utterance includes the particular,predefined hotword (230). The audio features of the audio data thatcorresponds to the utterance are extracted. In some implementations, thelikelihood that the utterance includes a hotword may be represented by ahotword confidence score. The hotword confidence score is generated byprocessing the audio features.

The hotword confidence score may be normalized to a scale from one toone where one indicates the highest likelihood that the utteranceincludes a hotword. The first computing device may compare the hotwordconfidence score to a hotword confidence threshold. If the hotwordconfidence score satisfies the hotword confidence threshold, the firstcomputing device may determine that the audio data that corresponds tothe utterance includes the particular, predefined hotword.

If the hotword confidence score does not satisfy the hotword confidencethreshold, then the system determines that the audio data does notinclude the hotword. For example, if the hotword confidence threshold is0.75, then audio data with a hotword confidence score above 0.75 wouldbe labeled as including the hotword and audio data with hotwordconfidence score below 0.75 would be labeled as not including thehotword.

In some implementations, the system determines that the audio dataincludes the hotword without performing speech recognition on the audiodata.

In some implementations, the first computing device determines thelikelihood that the utterance includes a particular, predefined hotwordby comparing the audio data of the utterance to a group of audio samplesthat include the hotword.

In some implementations, the first computing device receives dataindicating that the second computing device is responding to the audiodata (240). This could be data from a server, or from the secondcomputing device and through a local network indicating that the secondcomputing device is responding to the audio data. The data could be anotification signal such as an ultrasound, a short range radio signal,or a local area wireless signal to indicate that the second computingdevice is initiating speech recognition processing on the audio data. Toreceive the signal, the first computing device may ensure that themicrophone of the first computing device remains active, that a shortrange radio receiver is active, or that another radio such a local areawireless radio is active.

The first computing device receives a transcription of additional audiodata outputted by the second computing device in response to theutterance (250).

In some implementations, the second computing device may generate atranscription of additional audio data in response to the utteranceresponse to the received data based on user information that isassociated with the audio data. The user information may be associatedwith a user of the first computing device (e.g., calendar, contacts,media files, social media information, personal preferences, etc.).

For example, if Bob speaks the utterance “OK Computer, schedule ameeting with Bob this afternoon.”, computing device 104 b might useinformation from the calendar associated with Bob stored on thecomputing device 104 b to provide a suggestion for a meeting time andmay provide the response “Does either 3 or 4 pm work?”

The first computing device generates a transcription that corresponds toa response to the additional audio data based on the transcription ofthe additional audio data and the utterance (260).

In some implementations, one or more of the computing device 104 a and104 b may determine a location of the computing device, and use thelocation information to generate a response. For example, if computingdevice 104 a determines that it is in a place where it might beinappropriate to respond audibly, e.g., in a library, the computingdevice 104 a might not provide a response, or it may provide theresponse to the display 140 of the computing device 104A.

In some implementations, the computing device might access data that isassociated with the transcription of the additional audio data andgenerate the transcription based on the accessed data. For example, ifthe transcription of the additional audio data includes a query askingfor suggestions for restaurants in the vicinity, the computing devicemight perform a web search to access data corresponding to restaurantsnearby. The computing device may use this accessed data to generate thetranscription corresponding to the response.

The computing device provides, for output, the transcription thatcorresponds to the response (270). In some implementations, thisincludes providing the transcription that corresponds to the response toa speech synthesizer. The output of the speech synthesizer may beprovided to an audio speaker of the computing device.

In some implementations, the transcription that corresponds to theresponse may be provided to a display of the computing device.

In some implementations, collaboration among multiple devices might beused to improve the quality of speech recognition. Since differentdevices have different sensors (microphones), and are positioneddifferently in the user's surroundings, it could be that none of themcorrectly transcribed the whole user query but combining thetranscriptions of all the computing devices might match the queryperfectly. In another example, if a user is moving around a space, anddifferent computing devices are close to the user at different timesduring the speaking of the query, by using the transcriptions from eachof the computing devices and combining them, a more accuratetranscription may be obtained.

FIG. 3 shows an example of a computing device 300 and a mobile computingdevice 350 that can be used to implement the techniques described here.The computing device 300 is intended to represent various forms ofdigital computers, such as laptops, desktops, workstations, personaldigital assistants, servers, blade servers, mainframes, and otherappropriate computers. The mobile computing device 350 is intended torepresent various forms of mobile devices, such as personal digitalassistants, cellular telephones, smart-phones, and other similarcomputing devices. The components shown here, their connections andrelationships, and their functions, are meant to be examples only, andare not meant to be limiting.

The computing device 300 includes a processor 302, a memory 304, astorage device 306, a high-speed interface 308 connecting to the memory304 and multiple high-speed expansion ports 310, and a low-speedinterface 312 connecting to a low-speed expansion port 314 and thestorage device 306. Each of the processor 302, the memory 304, thestorage device 306, the high-speed interface 308, the high-speedexpansion ports 310, and the low-speed interface 312, are interconnectedusing various busses, and may be mounted on a common motherboard or inother manners as appropriate. The processor 302 can process instructionsfor execution within the computing device 300, including instructionsstored in the memory 304 or on the storage device 306 to displaygraphical information for a GUI on an external input/output device, suchas a display 316 coupled to the high-speed interface 308. In otherimplementations, multiple processors and/or multiple buses may be used,as appropriate, along with multiple memories and types of memory. Also,multiple computing devices may be connected, with each device providingportions of the necessary operations (e.g., as a server bank, a group ofblade servers, or a multi-processor system).

The memory 304 stores information within the computing device 300. Insome implementations, the memory 304 is a volatile memory unit or units.In some implementations, the memory 304 is a non-volatile memory unit orunits. The memory 304 may also be another form of computer-readablemedium, such as a magnetic or optical disk.

The storage device 306 is capable of providing mass storage for thecomputing device 300. In some implementations, the storage device 306may be or contain a computer-readable medium, such as a floppy diskdevice, a hard disk device, an optical disk device, or a tape device, aflash memory or other similar solid state memory device, or an array ofdevices, including devices in a storage area network or otherconfigurations. Instructions can be stored in an information carrier.The instructions, when executed by one or more processing devices (forexample, processor 302), perform one or more methods, such as thosedescribed above. The instructions can also be stored by one or morestorage devices such as computer- or machine-readable mediums (forexample, the memory 304, the storage device 306, or memory on theprocessor 302).

The high-speed interface 308 manages bandwidth-intensive operations forthe computing device 300, while the low-speed interface 312 manageslower bandwidth-intensive operations. Such allocation of functions is anexample only. In some implementations, the high-speed interface 308 iscoupled to the memory 304, the display 316 (e.g., through a graphicsprocessor or accelerator), and to the high-speed expansion ports 310,which may accept various expansion cards (not shown). In theimplementation, the low-speed interface 312 is coupled to the storagedevice 306 and the low-speed expansion port 314. The low-speed expansionport 314, which may include various communication ports (e.g., USB,Bluetooth, Ethernet, wireless Ethernet) may be coupled to one or moreinput/output devices, such as a keyboard, a pointing device, a scanner,or a networking device such as a switch or router, e.g., through anetwork adapter.

The computing device 300 may be implemented in a number of differentforms, as shown in the figure. For example, it may be implemented as astandard server 320, or multiple times in a group of such servers. Inaddition, it may be implemented in a personal computer such as a laptopcomputer 322. It may also be implemented as part of a rack server system324. Alternatively, components from the computing device 300 may becombined with other components in a mobile device (not shown), such as amobile computing device 350. Each of such devices may contain one ormore of the computing device 300 and the mobile computing device 350,and an entire system may be made up of multiple computing devicescommunicating with each other.

The mobile computing device 350 includes a processor 352, a memory 364,an input/output device such as a display 354, a communication interface366, and a transceiver 368, among other components. The mobile computingdevice 350 may also be provided with a storage device, such as amicro-drive or other device, to provide additional storage. Each of theprocessor 352, the memory 364, the display 354, the communicationinterface 366, and the transceiver 368, are interconnected using variousbuses, and several of the components may be mounted on a commonmotherboard or in other manners as appropriate.

The processor 352 can execute instructions within the mobile computingdevice 350, including instructions stored in the memory 364. Theprocessor 352 may be implemented as a chipset of chips that includeseparate and multiple analog and digital processors. The processor 352may provide, for example, for coordination of the other components ofthe mobile computing device 350, such as control of user interfaces,applications run by the mobile computing device 350, and wirelesscommunication by the mobile computing device 350.

The processor 352 may communicate with a user through a controlinterface 358 and a display interface 356 coupled to the display 354.The display 354 may be, for example, a TFT (Thin-Film-Transistor LiquidCrystal Display) display or an OLED (Organic Light Emitting Diode)display, or other appropriate display technology. The display interface356 may comprise appropriate circuitry for driving the display 354 topresent graphical and other information to a user. The control interface358 may receive commands from a user and convert them for submission tothe processor 352. In addition, an external interface 362 may providecommunication with the processor 352, so as to enable near areacommunication of the mobile computing device 350 with other devices. Theexternal interface 362 may provide, for example, for wired communicationin some implementations, or for wireless communication in otherimplementations, and multiple interfaces may also be used.

The memory 364 stores information within the mobile computing device350. The memory 364 can be implemented as one or more of acomputer-readable medium or media, a volatile memory unit or units, or anon-volatile memory unit or units. An expansion memory 374 may also beprovided and connected to the mobile computing device 350 through anexpansion interface 372, which may include, for example, a SIMM (SingleIn Line Memory Module) card interface. The expansion memory 374 mayprovide extra storage space for the mobile computing device 350, or mayalso store applications or other information for the mobile computingdevice 350. Specifically, the expansion memory 374 may includeinstructions to carry out or supplement the processes described above,and may include secure information also. Thus, for example, theexpansion memory 374 may be provide as a security module for the mobilecomputing device 350, and may be programmed with instructions thatpermit secure use of the mobile computing device 350. In addition,secure applications may be provided via the SIMM cards, along withadditional information, such as placing identifying information on theSIMM card in a non-hackable manner.

The memory may include, for example, flash memory and/or NVRAM memory(non-volatile random access memory), as discussed below. In someimplementations, instructions are stored in an information carrier suchthat the instructions, when executed by one or more processing devices(for example, processor 352), perform one or more methods, such as thosedescribed above. The instructions can also be stored by one or morestorage devices, such as one or more computer- or machine-readablemediums (for example, the memory 364, the expansion memory 374, ormemory on the processor 352). In some implementations, the instructionscan be received in a propagated signal, for example, over thetransceiver 368 or the external interface 362.

The mobile computing device 350 may communicate wirelessly through thecommunication interface 366, which may include digital signal processingcircuitry where necessary. The communication interface 366 may providefor communications under various modes or protocols, such as GSM voicecalls (Global System for Mobile communications), SMS (Short MessageService), EMS (Enhanced Messaging Service), or MMS messaging (MultimediaMessaging Service), CDMA (code division multiple access), TDMA (timedivision multiple access), PDC (Personal Digital Cellular), WCDMA(Wideband Code Division Multiple Access), CDMA2000, or GPRS (GeneralPacket Radio Service), among others. Such communication may occur, forexample, through the transceiver 368 using a radio-frequency. Inaddition, short-range communication may occur, such as using aBluetooth, WiFi, or other such transceiver (not shown). In addition, aGPS (Global Positioning System) receiver module 370 may provideadditional navigation- and location-related wireless data to the mobilecomputing device 350, which may be used as appropriate by applicationsrunning on the mobile computing device 350.

The mobile computing device 350 may also communicate audibly using anaudio codec 360, which may receive spoken information from a user andconvert it to usable digital information. The audio codec 360 maylikewise generate audible sound for a user, such as through a speaker,e.g., in a handset of the mobile computing device 350. Such sound mayinclude sound from voice telephone calls, may include recorded sound(e.g., voice messages, music files, etc.) and may also include soundgenerated by applications operating on the mobile computing device 350.

The mobile computing device 350 may be implemented in a number ofdifferent forms, as shown in the figure. For example, it may beimplemented as a cellular telephone 380. It may also be implemented aspart of a smart-phone 382, personal digital assistant, or other similarmobile device.

Various implementations of the systems and techniques described here canbe realized in digital electronic circuitry, integrated circuitry,specially designed ASICs (application specific integrated circuits),computer hardware, firmware, software, and/or combinations thereof.These various implementations can include implementation in one or morecomputer programs that are executable and/or interpretable on aprogrammable system including at least one programmable processor, whichmay be special or general purpose, coupled to receive data andinstructions from, and to transmit data and instructions to, a storagesystem, at least one input device, and at least one output device.

These computer programs (also known as programs, software, softwareapplications or code) include machine instructions for a programmableprocessor, and can be implemented in a high-level procedural and/orobject-oriented programming language, and/or in assembly/machinelanguage. As used herein, the terms machine-readable medium andcomputer-readable medium refer to any computer program product,apparatus and/or device (e.g., magnetic discs, optical disks, memory,Programmable Logic Devices (PLDs)) used to provide machine instructionsand/or data to a programmable processor, including a machine-readablemedium that receives machine instructions as a machine-readable signal.The term machine-readable signal refers to any signal used to providemachine instructions and/or data to a programmable processor.

To provide for interaction with a user, the systems and techniquesdescribed here can be implemented on a computer having a display device(e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor)for displaying information to the user and a keyboard and a pointingdevice (e.g., a mouse or a trackball) by which the user can provideinput to the computer. Other kinds of devices can be used to provide forinteraction with a user as well; for example, feedback provided to theuser can be any form of sensory feedback (e.g., visual feedback,auditory feedback, or tactile feedback); and input from the user can bereceived in any form, including acoustic, speech, or tactile input.

The systems and techniques described here can be implemented in acomputing system that includes a back end component (e.g., as a dataserver), or that includes a middleware component (e.g., an applicationserver), or that includes a front end component (e.g., a client computerhaving a graphical user interface or a Web browser through which a usercan interact with an implementation of the systems and techniquesdescribed here), or any combination of such back end, middleware, orfront end components. The components of the system can be interconnectedby any form or medium of digital data communication (e.g., acommunication network). Examples of communication networks include alocal area network (LAN), a wide area network (WAN), and the Internet.

The computing system can include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other.

Although a few implementations have been described in detail above,other modifications are possible. For example, while a clientapplication is described as accessing the delegate(s), in otherimplementations the delegate(s) may be employed by other applicationsimplemented by one or more processors, such as an application executingon one or more servers. In addition, the logic flows depicted in thefigures do not require the particular order shown, or sequential order,to achieve desirable results. In addition, other actions may beprovided, or actions may be eliminated, from the described flows, andother components may be added to, or removed from, the describedsystems. Accordingly, other implementations are within the scope of thefollowing claims.

What is claimed is:
 1. A computer-implemented method, comprising:identifying, by a first computing device, a second computing device thatis configured to respond to a particular, predefined hotword; receiving,by the first computing device, audio data of an utterance spoken by auser; determining, by the first computing device, that the utteranceincludes the particular, predefined hotword; receiving, by the firstcomputing device, a transcription of an initial response to theutterance provided by the second computing device, wherein the initialresponse comprises synthesized speech audibly outputted by the secondcomputing device; based on the transcription of the initial response andbased on the utterance, generating, by the first computing device, asubsequent response to the initial response; and providing, for outputby the first computing device, audio data of the subsequent response ora transcription of the subsequent response.
 2. The method of claim 1,wherein providing, for output, audio data of the subsequent response ora transcription of the subsequent response comprises: providing, to aspeech synthesizer of the first computing device, an initial portion ofthe transcription of the subsequent response; and providing, to thesecond computing device, (i) a remaining portion of the transcription ofthe subsequent response and (ii) instructions to audibly outputsynthesized speech of the remaining portion of the transcription of thesubsequent response.
 3. The method of claim 1, comprising: afterproviding, for output, the transcription that corresponds to theresponse, receiving, by the first computing device, audio data of asecond utterance; based on the transcription of the initial response,based on the utterance, and based on the second utterance, generating,by the first computing device, an additional transcription of anadditional response to the second utterance; and providing, for outputby the first computing device, the additional transcription.
 4. Themethod of claim 1, wherein providing, for output, audio data of thesubsequent response or a transcription of the subsequent responsecomprises: providing the transcription to a display of the firstcomputing device.
 5. The method of claim 1, wherein generating asubsequent response to the initial response comprises: determining userinformation that is associated with a first user of the first computingdevice or with a second user of the second computing device; and whereingenerating the subsequent response to the initial response is based onthe user information.
 6. The method of claim 1, wherein generatingsubsequent response to the initial response comprises: accessing datathat is associated with the initial response; and wherein generating thesubsequent response to the initial response is based on the accesseddata.
 7. The method of claim 1, comprising: determining, by the firstcomputing device, a location of the first computing device, whereingenerating the subsequent response to the initial response is based onthe location of the first computing device.
 8. The method of claim 1,comprising: generating, by the first computing device, a first audiofingerprint of the audio data of the utterance; receiving, from thesecond computing device, a second audio fingerprint of the audio data ofthe utterance; comparing, by the first computing device, the first audiofingerprint to the second audio fingerprint; and based on comparing thefirst audio fingerprint to the second audio fingerprint, determining, bythe first computing device, that the audio data received by the firstcomputing device represents the same utterance as the audio datareceived by the second computing device.
 9. The method of claim 1,wherein the first computing device and the second computing device areconfigured to communicate with each other using short range radio. 10.The method of claim 1, wherein the first computing device and the secondcomputing device are co-located.
 11. The method of claim 1, whereinreceiving the transcription of the initial response to the utteranceprovided by the second computing device comprises: receiving, from thesecond computing device, the transcription of the initial response tothe utterance provided by the second computing device.
 12. The method ofclaim 1, wherein providing, for output, audio data of the subsequentresponse or a transcription of the subsequent response comprises:providing the transcription the subsequent response to a speechsynthesizer.
 13. The method of claim 12, wherein synthesized speech of atranscription of the subsequent response is received by a thirdcomputing device that is configured to generate a response based on thesynthesized speech of the transcription of the subsequent response, thetranscription of the initial response, and the utterance.
 14. The methodof claim 1, comprising: determining that the utterance includes theparticular, predefined hotword by: determining that the utteranceincludes the particular, predefined hotword without preforming speechrecognition on the audio data; and receiving data indicating that thesecond computing device will output the initial response to theutterance.
 15. The method of claim 14, comprising: receiving dataindicating that the second computing device will output the initialresponse to the utterance by: receiving, from the second computingdevice, a short range radio signal that indicates that the secondcomputing device will output the initial response to the utterance;receiving, from the second computing device and through a local network,data indicating that the second computing device will output the initialresponse to the utterance; or receiving, from a server, data indicatingthat the second computing device will output the initial response to theutterance.
 16. The method of claim 14, wherein determining that theutterance includes the particular, predefined hotword without preformingspeech recognition on the audio data comprises: extracting audiofeatures of the audio data of the utterance; generating a hotwordconfidence score by processing the audio features; determining that thehotword confidence score satisfies a hotword confidence threshold; andbased on determining that the hotword confidence score satisfies ahotword confidence threshold, determining that the utterance includesthe particular, predefined hotword.
 17. The method of claim 15,comprising: in response to receiving data indicating that the secondcomputing device will output the initial response to the utterance,providing, by the first computing device and to the second computingdevice or to a server, the audio data of the utterance.
 18. A systemcomprising: one or more computers and one or more storage devicesstoring instructions that are operable, when executed by the one or morecomputers, to cause the one or more computers to perform operationscomprising: identifying, by a first computing device, a second computingdevice that is configured to respond to a particular, predefinedhotword; receiving, by the first computing device, audio data of anutterance spoken by a user; determining, by the first computing device,that the utterance includes the particular, predefined hotword;receiving, by the first computing device, a transcription of an initialresponse to the utterance provided by the second computing device,wherein the initial response comprises synthesized speech audiblyoutputted by the second computing device; based on the transcription ofthe initial response and based on the utterance, generating, by thefirst computing device, a subsequent response to the initial response;and providing, for output by the first computing device, audio data ofthe subsequent response or a transcription of the subsequent response.19. A non-transitory computer-readable medium storing softwarecomprising instructions executable by one or more computers which, uponsuch execution, cause the one or more computers to perform operationscomprising: identifying, by a first computing device, a second computingdevice that is configured to respond to a particular, predefinedhotword; receiving, by the first computing device, audio data of anutterance spoken by a user; determining, by the first computing device,that the utterance includes the particular, predefined hotword;receiving, by the first computing device, a transcription of an initialresponse to the utterance provided by the second computing device,wherein the initial response comprises synthesized speech audiblyoutputted by the second computing device; based on the transcription ofthe initial response and based on the utterance, generating, by thefirst computing device, a subsequent response to the initial response;and providing, for output by the first computing device, audio data ofthe subsequent response or a transcription of the subsequent response.